Wind Energy - 3-B-3-Veers-Blade reliability...

2008 Wind Turbine Blade Workshop, Albuquerque, NM

Blade Reliability Initiative

Paul VeersSandia National Laboratories

Blade WorkshopAlbuquerque, New Mexico

14-May-2008


Reliability is the key focus of the industry

At EWEC 2008, the industry CEOs spoke with a common voice that the focus would be on improving the reliability of the current product line rather than innovating on the product.Reliability is a system issueReliability solutions are effected at the component level

Reliability The number-one key word for Vestas

Reliability: The performance standard for a maturing industry.

Vestas CEO quote (Windpower Monthly): “Our number one goal is no longer market share, it is reliability.”

Vestas, 3rd quarter report, 2007


Blade Reliability

Blades are being delivered to the site in a condition that often requires additional treatment of quality issues before they can be installedRare installations need to have all the blades replaced after the discovery of a batch problem

Blade failure can cause extensive down time and lead to expensive repairs.

Blade reliability issues need early attention because of the lost production and cost of significant failures

“80% of the blades that require repair have never been flown.”

Gary Kanaby, Knight & Carver Wind Blade Division.

Drive Train

Supporting Structure /Housing

Generator

Gearbox

Rotor Hub

Mechanical Brake

Rotor Blades

Yaw System

Hydraulic System

Sensors

Electronic Control

Electrical System

Down time per failure (in days)Annual failure frequency 1 0,75 0,5 0,25 0 2 4 6 8

ISET

Blades are in the middle – medium failure rate, relatively high cost.US environments may be more aggressive.

Historical European Experience (Paul Kühn, ISET)


“Delphi” Expert’s Group Assessment of Issues

Experts from Industry, consulting, academia, and national labs convened to identify critical issues (few numbers)Collected expert knowledge as a basis for planning to address blade reliability needs


Preliminary Survey of Operators - 2008

Five Plants – over 400 turbinesMostly 3+ years oldAbout 80 blade replacements – 40 (half) at one plantReplacement times range from 2 weeks to 2 monthsBlade Issues Cited:• Manufacturing Issues – waviness and

overlaid laminates• Bad bonds, Delamination, and Voids• Leading Edge Erosion• Trailing Edge Splits• Lightning – Comments:

At one plant - Every blade has been struck at least onceMany repairs and replacementsScorching and splitsManageable problem (relative to gearboxes)

Knight & Carver

Knight & Carver

Roger Hill


Major Issues for Improved Blade ReliabilityIdentified by the “Delphi” Group

1. Infusion Quality2. Bonding Quality3. Inspection Capability4. Environmental Protection5. Multiple Assembly Plants or Assembly Lines6. Certification, Tracking and Feedback

Six threads of issues


1. Infusion (composite fabrication) Quality

Complete infusion, voidsFibers moving during infusion prior to curing (waviness)Material drop off – DetailingSpeed of production creates problemsScaling issues

1/2 meter

Waviness

Delaminations

Carbon Spar Cap


2. Bonding Quality

Typical Blade Bond Lines• Difficult to control• Blind bonds• Scaling effects

Shear-Web BondingBond-Line VoidsBond-Line Weakness (without major voids)Commentary from a Blade Manufacturing Manager• “The most difficult part of manufacturing process is trying to

bond the two shells together.”• “Trailing edge defects can grow to full blade failure.”• “Bonding problems are the biggest issue.”

Minor Voids


3. Environmental Protection

Leading edge erosionMoisture intrusionFreeze/Thaw cyclingRoot fastener corrosionLightning• Big issue• Many blades are repaired• Some operators consider it

manageable - when compared to other components, such as gear boxes

Knight & Carver

Severe Leading Edge Erosion

Knight & Carver

Lightning Strike


4. Inspection Capability: Factory and Field

Existing inspection methods can detect bond line gaps and major delaminationsEvery blade manufacturer has inspection methods but some problems are still getting throughNeed to know what inspection methods are effective at finding the flaws that affect early failure.

Phased Array UT Inspection of an Aircraft Vertical Stabilizer SpecimenAircraft Example

Carbon Panel

(bonded ribs)

Sandia AANC


5. Multiple Assembly Plants

Not covered in standardsProduction start-up (infant mortality) Local practices and corporate culturesProcess qualification – metrics, procedures, etc.Bad batches of blades • lead to major plant development delays and cost

overruns• May not be reflected in operator surveys

because they are incurred before the transfer of responsibility from developer to operator

Vientek

LM Glassfiber

Courtesy Billy Roeseler, Boeing


6. Certification, Tracking and Feedback

RegulatoryActions

Fleet Surveillance

Design

Fabrication

CustomerSupport

Maintenance

Inspection

RepairReporting

Airplane manufacturer

Airline operators

Airworthiness authorities

Structuralsafety

Everyone takes ownership and has a role

Example of a Mature, High-Reliability, Structural Safety System

Commercial Aircraft

Involves regulatory authorities in the operations of the fleet, AND …Specific requirements would probably be too expensive for wind turbine application, BUT…

Continuous feedback to ManufacturersDrives component specification

How do we define a structure that provides the

benefits without the unnecessary overhead and

excessive cost?

☺


Blade Reliability Initiative – Three Phases

Discovery – Define the nature and extent of the issues: Focused on field work and full-scale testing

Evaluation – Characterize the issues and evaluate mitigation: Focused on laboratory testing and inspection

Resolution – Validate the methods of resolving specific issues: Targeted R&D to solve specific problems

Discovery

Evaluation

Resolution

LM Glassfiber

Time


Discovery Phase

National Reliability Database analysisOperator surveysField failure assessments and root cause analysisManufacturer inputs Evaluate Current inspection capabilityFull-scale blade testing: Fatigue tests reveal hidden flaws• Production blades• Detailed inspection• Typical manufacturing quality resulting capability

Knight & Carver

What is causing early field failures and unreliability?Field experience – Manufacturing Output

The inspection link between the two

LM Glassfiber


Evaluation Phase

Improvement and validation of analytical modeling and failure of as-built bladesSubcomponent testing of troublesome detailsEvaluating the impact of defects (coupon and substructure)Targeted Inspection method improvement• Specimens with well

characterized flaws• Actual flawed blades• Blind trial opportunities for

commercial inspection providers and blade manufacturers

Pursuing specific findings from the Discovery Phase.Fully define the issue.


Technology for inspection is evolving for new aircraft

The Boeing 787 is 50% composite material in structural elementsComposite Inspection is growing in technical sophisticationTied to damage tolerance

Composite Structures on Boeing 787 Aircraft

Carbon laminateCarbon sandwichFiberglassAluminumAluminum/steel/titanium pylons

Composites50%

Aluminum20%

Titanium15%

Steel10%

Other5%

Nondestructive Inspection

Detectable Flaw Size1 2 3 4 5 6 7 8 9 10

Allowable Flaw SizeDamage Tolerance

1 2 3 4 5 6 7 8 9 10


Flaw templates - ensure proper location of flaws

Flawsinserted

Example: Fabricated flaws for validation of inspection

Sandia’s AANC


Resolution Phase

Outcome: Definition of the Critical Issues

Confirm the level of quality required to preempt the delivery of flawed blades to the fieldValidate the inspection methods capable of certifying the required quality

Long-Term Effect: Drive the R&D agenda

R&D will be issue specific and led by manufacturersInnovation will have a reliability driver

Pursue design changes to eliminate the root causes “Failure Modes and Effects Avoidance”


Questions?

Thank You

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